The volcano lies around 70km (40 miles) from Mexico City, and is visible from the capital on a clear day.

"We can hear the roar of the volcano, sometimes we can feel its force," Concepcion Perez from the town of Xalitzintla in Puebla State, 12km (seven miles) from the volcano told the French news agency Agence France-Presse.

Cenapred officials said the alert could remain for weeks or months until the volcano's activity diminished.